调整图像大小时保持纵横比

Question

以下脚本用于调整图像大小。但是，我希望能够定义宽度，然后按比例调整图像大小并保持宽高比。

这是我的代码。

的index.php

<?php
include( 'function.php');
// settings
$max_file_size = 1024*200; // 200kb
$valid_exts = array('jpeg', 'jpg', 'png', 'gif');
// thumbnail sizes
$sizes = array(100 => 100, 150 => 150, 250 => 250);

if ($_SERVER['REQUEST_METHOD'] == 'POST' AND isset($_FILES['image'])) {
  if( $_FILES['image']['size'] < $max_file_size ){
    // get file extension
    $ext = strtolower(pathinfo($_FILES['image']['name'], PATHINFO_EXTENSION));
    if (in_array($ext, $valid_exts)) {
      /* resize image */
      foreach ($sizes as $w => $h) {
        $files[] = resize($w, $h);
      }

    } else {
      $msg = 'Unsupported file';
    }
  } else{
    $msg = 'Please upload image smaller than 200KB';
  }
}
?>

的functions.php

/**
 * Image resize
 * @param int $width
 * @param int $height
 */
function resize($width, $height){
  /* Get original image x y*/
  list($w, $h) = getimagesize($_FILES['image']['tmp_name']);
  /* calculate new image size with ratio */
  $ratio = max($width/$w, $height/$h);
  $h = ceil($height / $ratio);
  $x = ($w - $width / $ratio) / 2;
  $w = ceil($width / $ratio);
  /* new file name */
  $path = 'uploads/'.$width.'x'.$height.'_'.$_FILES['image']['name'];
  /* read binary data from image file */
  $imgString = file_get_contents($_FILES['image']['tmp_name']);
  /* create image from string */
  $image = imagecreatefromstring($imgString);
  $tmp = imagecreatetruecolor($width, $height);
  imagecopyresampled($tmp, $image,
    0, 0,
    $x, 0,
    $width, $height,
    $w, $h);
  /* Save image */
  switch ($_FILES['image']['type']) {
    case 'image/jpeg':
      imagejpeg($tmp, $path, 100);
      break;
    case 'image/png':
      imagepng($tmp, $path, 0);
      break;
    case 'image/gif':
      imagegif($tmp, $path);
      break;
    default:
      exit;
      break;
  }
  return $path;
  /* cleanup memory */
  imagedestroy($image);
  imagedestroy($tmp);
}

我该怎么办？在这个领域没有那么多经验，所以指南或例子会很棒。一切都很贴心！提前谢谢。